(function (global) {
    "use strict";

    /* Set up a RequestAnimationFrame shim so we can animate efficiently FOR
     * GREAT JUSTICE. */
    var requestInterval, cancelInterval;

    (function () {
        var raf = global.requestAnimationFrame ||
            global.webkitRequestAnimationFrame ||
            global.mozRequestAnimationFrame ||
            global.oRequestAnimationFrame ||
            global.msRequestAnimationFrame,
            caf = global.cancelAnimationFrame ||
                global.webkitCancelAnimationFrame ||
                global.mozCancelAnimationFrame ||
                global.oCancelAnimationFrame ||
                global.msCancelAnimationFrame;

        if (raf && caf) {
            requestInterval = function (fn, delay) {
                var handle = {value: null};

                function loop() {
                    handle.value = raf(loop);
                    fn();
                }

                loop();
                return handle;
            };

            cancelInterval = function (handle) {
                caf(handle.value);
            };
        } else {
            requestInterval = setInterval;
            cancelInterval = clearInterval;
        }
    }());
    /* Define skycon things. */
    /* FIXME: I'm *really really* sorry that this code is so gross. Really, I am.
     * I'll try to clean it up eventually! Promise! */
    var KEYFRAME = 500,
        STROKE = 0.08,
        TAU = 2.0 * Math.PI,
        TWO_OVER_SQRT_2 = 2.0 / Math.sqrt(2);

    function circle(ctx, x, y, r) {
        ctx.beginPath();
        ctx.arc(x, y, r, 0, TAU, false);
        ctx.fill();
    }

    function line(ctx, ax, ay, bx, by) {
        ctx.beginPath();
        ctx.moveTo(ax, ay);
        ctx.lineTo(bx, by);
        ctx.stroke();
    }

    function puff(ctx, t, cx, cy, rx, ry, rmin, rmax) {
        var c = Math.cos(t * TAU),
            s = Math.sin(t * TAU);

        rmax -= rmin;

        circle(
            ctx,
            cx - s * rx,
            cy + c * ry + rmax * 0.5,
            rmin + (1 - c * 0.5) * rmax
        );
    }

    function puffs(ctx, t, cx, cy, rx, ry, rmin, rmax) {
        var i;

        for (i = 5; i--;)
            puff(ctx, t + i / 5, cx, cy, rx, ry, rmin, rmax);
    }

    function cloud(ctx, t, cx, cy, cw, s, color) {
        t /= 30000;

        var a = cw * 0.21,
            b = cw * 0.12,
            c = cw * 0.24,
            d = cw * 0.28;

        ctx.fillStyle = color;
        puffs(ctx, t, cx, cy, a, b, c, d);

        ctx.globalCompositeOperation = 'destination-out';
        puffs(ctx, t, cx, cy, a, b, c - s, d - s);
        ctx.globalCompositeOperation = 'source-over';
    }

    function sun(ctx, t, cx, cy, cw, s, color) {
        t /= 40000;

        var a = cw * 0.25 - s * 0.5,
            b = cw * 0.32 + s * 0.5,
            c = cw * 0.50 - s * 0.5,
            i, p, cos, sin;

        ctx.strokeStyle = color;
        ctx.lineWidth = s;
        ctx.lineCap = "round";
        ctx.lineJoin = "round";

        ctx.beginPath();
        ctx.arc(cx, cy, a, 0, TAU, false);
        ctx.stroke();

        for (i = 8; i--;) {
            p = (t + i / 8) * TAU;
            cos = Math.cos(p);
            sin = Math.sin(p);
            line(ctx, cx + cos * b, cy + sin * b, cx + cos * c, cy + sin * c);
        }
    }

    function moon(ctx, t, cx, cy, cw, s, color) {
        t /= 15000;

        var a = cw * 0.29 - s * 0.5,
            b = cw * 0.05,
            c = Math.cos(t * TAU),
            p = c * TAU / -16;

        ctx.strokeStyle = color;
        ctx.lineWidth = s;
        ctx.lineCap = "round";
        ctx.lineJoin = "round";

        cx += c * b;

        ctx.beginPath();
        ctx.arc(cx, cy, a, p + TAU / 8, p + TAU * 7 / 8, false);
        ctx.arc(cx + Math.cos(p) * a * TWO_OVER_SQRT_2, cy + Math.sin(p) * a * TWO_OVER_SQRT_2, a, p + TAU * 5 / 8, p + TAU * 3 / 8, true);
        ctx.closePath();
        ctx.stroke();
    }

    function rain(ctx, t, cx, cy, cw, s, color) {
        t /= 1350;

        var a = cw * 0.16,
            b = TAU * 11 / 12,
            c = TAU * 7 / 12,
            i, p, x, y;

        ctx.fillStyle = color;

        for (i = 4; i--;) {
            p = (t + i / 4) % 1;
            x = cx + ((i - 1.5) / 1.5) * (i === 1 || i === 2 ? -1 : 1) * a;
            y = cy + p * p * cw;
            ctx.beginPath();
            ctx.moveTo(x, y - s * 1.5);
            ctx.arc(x, y, s * 0.75, b, c, false);
            ctx.fill();
        }
    }

    function sleet(ctx, t, cx, cy, cw, s, color) {
        t /= 750;

        var a = cw * 0.1875,
            b = TAU * 11 / 12,
            c = TAU * 7 / 12,
            i, p, x, y;

        ctx.strokeStyle = color;
        ctx.lineWidth = s * 0.5;
        ctx.lineCap = "round";
        ctx.lineJoin = "round";

        for (i = 4; i--;) {
            p = (t + i / 4) % 1;
            x = Math.floor(cx + ((i - 1.5) / 1.5) * (i === 1 || i === 2 ? -1 : 1) * a) + 0.5;
            y = cy + p * cw;
            line(ctx, x, y - s * 1.5, x, y + s * 1.5);
        }
    }

    function snow(ctx, t, cx, cy, cw, s, color) {
        t /= 3000;

        var a = cw * 0.16,
            b = s * 0.75,
            u = t * TAU * 0.7,
            ux = Math.cos(u) * b,
            uy = Math.sin(u) * b,
            v = u + TAU / 3,
            vx = Math.cos(v) * b,
            vy = Math.sin(v) * b,
            w = u + TAU * 2 / 3,
            wx = Math.cos(w) * b,
            wy = Math.sin(w) * b,
            i, p, x, y;

        ctx.strokeStyle = color;
        ctx.lineWidth = s * 0.5;
        ctx.lineCap = "round";
        ctx.lineJoin = "round";

        for (i = 4; i--;) {
            p = (t + i / 4) % 1;
            x = cx + Math.sin((p + i / 4) * TAU) * a;
            y = cy + p * cw;

            line(ctx, x - ux, y - uy, x + ux, y + uy);
            line(ctx, x - vx, y - vy, x + vx, y + vy);
            line(ctx, x - wx, y - wy, x + wx, y + wy);
        }
    }

    function fogbank(ctx, t, cx, cy, cw, s, color) {
        t /= 30000;

        var a = cw * 0.21,
            b = cw * 0.06,
            c = cw * 0.21,
            d = cw * 0.28;

        ctx.fillStyle = color;
        puffs(ctx, t, cx, cy, a, b, c, d);

        ctx.globalCompositeOperation = 'destination-out';
        puffs(ctx, t, cx, cy, a, b, c - s, d - s);
        ctx.globalCompositeOperation = 'source-over';
    }

    /*
    var WIND_PATHS = [
          downsample(63, upsample(8, [
            -1.00, -0.28,
            -0.75, -0.18,
            -0.50,  0.12,
            -0.20,  0.12,
            -0.04, -0.04,
            -0.07, -0.18,
            -0.19, -0.18,
            -0.23, -0.05,
            -0.12,  0.11,
             0.02,  0.16,
             0.20,  0.15,
             0.50,  0.07,
             0.75,  0.18,
             1.00,  0.28
          ])),
          downsample(31, upsample(16, [
            -1.00, -0.10,
            -0.75,  0.00,
            -0.50,  0.10,
            -0.25,  0.14,
             0.00,  0.10,
             0.25,  0.00,
             0.50, -0.10,
             0.75, -0.14,
             1.00, -0.10
          ]))
        ];
    */

    var WIND_PATHS = [
            [
                -0.7500, -0.1800, -0.7219, -0.1527, -0.6971, -0.1225,
                -0.6739, -0.0910, -0.6516, -0.0588, -0.6298, -0.0262,
                -0.6083, 0.0065, -0.5868, 0.0396, -0.5643, 0.0731,
                -0.5372, 0.1041, -0.5033, 0.1259, -0.4662, 0.1406,
                -0.4275, 0.1493, -0.3881, 0.1530, -0.3487, 0.1526,
                -0.3095, 0.1488, -0.2708, 0.1421, -0.2319, 0.1342,
                -0.1943, 0.1217, -0.1600, 0.1025, -0.1290, 0.0785,
                -0.1012, 0.0509, -0.0764, 0.0206, -0.0547, -0.0120,
                -0.0378, -0.0472, -0.0324, -0.0857, -0.0389, -0.1241,
                -0.0546, -0.1599, -0.0814, -0.1876, -0.1193, -0.1964,
                -0.1582, -0.1935, -0.1931, -0.1769, -0.2157, -0.1453,
                -0.2290, -0.1085, -0.2327, -0.0697, -0.2240, -0.0317,
                -0.2064, 0.0033, -0.1853, 0.0362, -0.1613, 0.0672,
                -0.1350, 0.0961, -0.1051, 0.1213, -0.0706, 0.1397,
                -0.0332, 0.1512, 0.0053, 0.1580, 0.0442, 0.1624,
                0.0833, 0.1636, 0.1224, 0.1615, 0.1613, 0.1565,
                0.1999, 0.1500, 0.2378, 0.1402, 0.2749, 0.1279,
                0.3118, 0.1147, 0.3487, 0.1015, 0.3858, 0.0892,
                0.4236, 0.0787, 0.4621, 0.0715, 0.5012, 0.0702,
                0.5398, 0.0766, 0.5768, 0.0890, 0.6123, 0.1055,
                0.6466, 0.1244, 0.6805, 0.1440, 0.7147, 0.1630,
                0.7500, 0.1800
            ],
            [
                -0.7500, 0.0000, -0.7033, 0.0195, -0.6569, 0.0399,
                -0.6104, 0.0600, -0.5634, 0.0789, -0.5155, 0.0954,
                -0.4667, 0.1089, -0.4174, 0.1206, -0.3676, 0.1299,
                -0.3174, 0.1365, -0.2669, 0.1398, -0.2162, 0.1391,
                -0.1658, 0.1347, -0.1157, 0.1271, -0.0661, 0.1169,
                -0.0170, 0.1046, 0.0316, 0.0903, 0.0791, 0.0728,
                0.1259, 0.0534, 0.1723, 0.0331, 0.2188, 0.0129,
                0.2656, -0.0064, 0.3122, -0.0263, 0.3586, -0.0466,
                0.4052, -0.0665, 0.4525, -0.0847, 0.5007, -0.1002,
                0.5497, -0.1130, 0.5991, -0.1240, 0.6491, -0.1325,
                0.6994, -0.1380, 0.7500, -0.1400
            ]
        ],
        WIND_OFFSETS = [
            {start: 0.36, end: 0.11},
            {start: 0.56, end: 0.16}
        ];

    function leaf(ctx, t, x, y, cw, s, color) {
        var a = cw / 8,
            b = a / 3,
            c = 2 * b,
            d = (t % 1) * TAU,
            e = Math.cos(d),
            f = Math.sin(d);

        ctx.fillStyle = color;
        ctx.strokeStyle = color;
        ctx.lineWidth = s;
        ctx.lineCap = "round";
        ctx.lineJoin = "round";

        ctx.beginPath();
        ctx.arc(x, y, a, d, d + Math.PI, false);
        ctx.arc(x - b * e, y - b * f, c, d + Math.PI, d, false);
        ctx.arc(x + c * e, y + c * f, b, d + Math.PI, d, true);
        ctx.globalCompositeOperation = 'destination-out';
        ctx.fill();
        ctx.globalCompositeOperation = 'source-over';
        ctx.stroke();
    }

    function swoosh(ctx, t, cx, cy, cw, s, index, total, color) {
        t /= 2500;

        var path = WIND_PATHS[index],
            a = (t + index - WIND_OFFSETS[index].start) % total,
            c = (t + index - WIND_OFFSETS[index].end) % total,
            e = (t + index) % total,
            b, d, f, i;

        ctx.strokeStyle = color;
        ctx.lineWidth = s;
        ctx.lineCap = "round";
        ctx.lineJoin = "round";

        if (a < 1) {
            ctx.beginPath();

            a *= path.length / 2 - 1;
            b = Math.floor(a);
            a -= b;
            b *= 2;
            b += 2;

            ctx.moveTo(
                cx + (path[b - 2] * (1 - a) + path[b] * a) * cw,
                cy + (path[b - 1] * (1 - a) + path[b + 1] * a) * cw
            );

            if (c < 1) {
                c *= path.length / 2 - 1;
                d = Math.floor(c);
                c -= d;
                d *= 2;
                d += 2;

                for (i = b; i !== d; i += 2)
                    ctx.lineTo(cx + path[i] * cw, cy + path[i + 1] * cw);

                ctx.lineTo(
                    cx + (path[d - 2] * (1 - c) + path[d] * c) * cw,
                    cy + (path[d - 1] * (1 - c) + path[d + 1] * c) * cw
                );
            } else
                for (i = b; i !== path.length; i += 2)
                    ctx.lineTo(cx + path[i] * cw, cy + path[i + 1] * cw);

            ctx.stroke();
        } else if (c < 1) {
            ctx.beginPath();

            c *= path.length / 2 - 1;
            d = Math.floor(c);
            c -= d;
            d *= 2;
            d += 2;

            ctx.moveTo(cx + path[0] * cw, cy + path[1] * cw);

            for (i = 2; i !== d; i += 2)
                ctx.lineTo(cx + path[i] * cw, cy + path[i + 1] * cw);

            ctx.lineTo(
                cx + (path[d - 2] * (1 - c) + path[d] * c) * cw,
                cy + (path[d - 1] * (1 - c) + path[d + 1] * c) * cw
            );

            ctx.stroke();
        }

        if (e < 1) {
            e *= path.length / 2 - 1;
            f = Math.floor(e);
            e -= f;
            f *= 2;
            f += 2;

            leaf(
                ctx,
                t,
                cx + (path[f - 2] * (1 - e) + path[f] * e) * cw,
                cy + (path[f - 1] * (1 - e) + path[f + 1] * e) * cw,
                cw,
                s,
                color
            );
        }
    }

    var Skycons = function (opts) {
        this.list = [];
        this.interval = null;
        this.color = opts && opts.color ? opts.color : "black";
        this.resizeClear = !!(opts && opts.resizeClear);
    };

    Skycons.CLEAR_DAY = function (ctx, t, color) {
        var w = ctx.canvas.width,
            h = ctx.canvas.height,
            s = Math.min(w, h);

        sun(ctx, t, w * 0.5, h * 0.5, s, s * STROKE, color);
    };

    Skycons.CLEAR_NIGHT = function (ctx, t, color) {
        var w = ctx.canvas.width,
            h = ctx.canvas.height,
            s = Math.min(w, h);

        moon(ctx, t, w * 0.5, h * 0.5, s, s * STROKE, color);
    };

    Skycons.PARTLY_CLOUDY_DAY = function (ctx, t, color) {
        var w = ctx.canvas.width,
            h = ctx.canvas.height,
            s = Math.min(w, h);

        sun(ctx, t, w * 0.625, h * 0.375, s * 0.75, s * STROKE, color);
        cloud(ctx, t, w * 0.375, h * 0.625, s * 0.75, s * STROKE, color);
    };

    Skycons.PARTLY_CLOUDY_NIGHT = function (ctx, t, color) {
        var w = ctx.canvas.width,
            h = ctx.canvas.height,
            s = Math.min(w, h);

        moon(ctx, t, w * 0.667, h * 0.375, s * 0.75, s * STROKE, color);
        cloud(ctx, t, w * 0.375, h * 0.625, s * 0.75, s * STROKE, color);
    };

    Skycons.CLOUDY = function (ctx, t, color) {
        var w = ctx.canvas.width,
            h = ctx.canvas.height,
            s = Math.min(w, h);

        cloud(ctx, t, w * 0.5, h * 0.5, s, s * STROKE, color);
    };

    Skycons.RAIN = function (ctx, t, color) {
        var w = ctx.canvas.width,
            h = ctx.canvas.height,
            s = Math.min(w, h);

        rain(ctx, t, w * 0.5, h * 0.37, s * 0.9, s * STROKE, color);
        cloud(ctx, t, w * 0.5, h * 0.37, s * 0.9, s * STROKE, color);
    };

    Skycons.SLEET = function (ctx, t, color) {
        var w = ctx.canvas.width,
            h = ctx.canvas.height,
            s = Math.min(w, h);

        sleet(ctx, t, w * 0.5, h * 0.37, s * 0.9, s * STROKE, color);
        cloud(ctx, t, w * 0.5, h * 0.37, s * 0.9, s * STROKE, color);
    };

    Skycons.SNOW = function (ctx, t, color) {
        var w = ctx.canvas.width,
            h = ctx.canvas.height,
            s = Math.min(w, h);

        snow(ctx, t, w * 0.5, h * 0.37, s * 0.9, s * STROKE, color);
        cloud(ctx, t, w * 0.5, h * 0.37, s * 0.9, s * STROKE, color);
    };

    Skycons.WIND = function (ctx, t, color) {
        var w = ctx.canvas.width,
            h = ctx.canvas.height,
            s = Math.min(w, h);

        swoosh(ctx, t, w * 0.5, h * 0.5, s, s * STROKE, 0, 2, color);
        swoosh(ctx, t, w * 0.5, h * 0.5, s, s * STROKE, 1, 2, color);
    };

    Skycons.FOG = function (ctx, t, color) {
        var w = ctx.canvas.width,
            h = ctx.canvas.height,
            s = Math.min(w, h),
            k = s * STROKE;

        fogbank(ctx, t, w * 0.5, h * 0.32, s * 0.75, k, color);

        t /= 5000;

        var a = Math.cos((t) * TAU) * s * 0.02,
            b = Math.cos((t + 0.25) * TAU) * s * 0.02,
            c = Math.cos((t + 0.50) * TAU) * s * 0.02,
            d = Math.cos((t + 0.75) * TAU) * s * 0.02,
            n = h * 0.936,
            e = Math.floor(n - k * 0.5) + 0.5,
            f = Math.floor(n - k * 2.5) + 0.5;

        ctx.strokeStyle = color;
        ctx.lineWidth = k;
        ctx.lineCap = "round";
        ctx.lineJoin = "round";

        line(ctx, a + w * 0.2 + k * 0.5, e, b + w * 0.8 - k * 0.5, e);
        line(ctx, c + w * 0.2 + k * 0.5, f, d + w * 0.8 - k * 0.5, f);
    };

    Skycons.prototype = {
        _determineDrawingFunction: function (draw) {
            if (typeof draw === "string")
                draw = Skycons[draw.toUpperCase().replace(/-/g, "_")] || null;

            return draw;
        },
        add: function (el, draw) {
            var obj;

            if (typeof el === "string")
                el = document.getElementById(el);

            // Does nothing if canvas name doesn't exists
            if (el === null)
                return;

            draw = this._determineDrawingFunction(draw);

            // Does nothing if the draw function isn't actually a function
            if (typeof draw !== "function")
                return;

            obj = {
                element: el,
                context: el.getContext("2d"),
                drawing: draw
            };

            this.list.push(obj);
            this.draw(obj, KEYFRAME);
        },
        set: function (el, draw) {
            var i;

            if (typeof el === "string")
                el = document.getElementById(el);

            for (i = this.list.length; i--;)
                if (this.list[i].element === el) {
                    this.list[i].drawing = this._determineDrawingFunction(draw);
                    this.draw(this.list[i], KEYFRAME);
                    return;
                }

            this.add(el, draw);
        },
        remove: function (el) {
            var i;

            if (typeof el === "string")
                el = document.getElementById(el);

            for (i = this.list.length; i--;)
                if (this.list[i].element === el) {
                    this.list.splice(i, 1);
                    return;
                }
        },
        draw: function (obj, time) {
            var canvas = obj.context.canvas;

            if (this.resizeClear)
                canvas.width = canvas.width;

            else
                obj.context.clearRect(0, 0, canvas.width, canvas.height);

            obj.drawing(obj.context, time, this.color);
        },
        play: function () {
            var self = this;

            this.pause();
            this.interval = requestInterval(function () {
                var now = Date.now(),
                    i;

                for (i = self.list.length; i--;)
                    self.draw(self.list[i], now);
            }, 1000 / 60);
        },
        pause: function () {
            var i;

            if (this.interval) {
                cancelInterval(this.interval);
                this.interval = null;
            }
        }
    };

    global.Skycons = Skycons;
}(this));
